So a somewhat simplistic take on this is that the CNNs are lazily prioritising texture when they ought to be prioritising something else, and a sophomoric reaction would be to decide that basic shape should be prioritised instead - and given what's been said about different angles and viewpoints, the word 'topology' comes to mind. But hold! - topologically, a teacup is identical to a donut. So this isn't so straightforward. This is going to involve proportion as well as shape, and texture, and the researchers behind these schemes are going to have to think hard about how to get the systems to take the hint, presumably without it being made explicit. Interesting challenge.